https://pinside.com/pinball/forum/topic/thinking-of-buying-an-em-buyers-guide
I made this post at the end of last year, hope it helps.

Since then I've bought 14 EMs and sold 7. My advice:
1. play many and allow yourself to change your mind.
2. Befriend em folks
3. By quality cosmetics
4. Don't over pay. Pins are veryveryvery easy to buy, but can be difficult to sell.
5. Don't give up on 2" flippers. For me it gives a very nice contrast to my more modern pins. I also found that if I want to use big flippers I'll play a dmd. 2" flippers are different and provide good challenge.
6. Learn to rebuild. Pensive, pinwiki, and pinrepair are great resources.
7. Do what DirtFlipper says . I am convinced he is always right. I wouldn't have bought all these and then sold them if I had listened to what he told me last year. I guess I am just one of those people who insist on making their own mistakes.

Good luck!

I started with that era. Sold them all and went to 60s!

100% disagree! My first 5+ pins were DMDs.

I admit it took me a few before I found what I liked, but I also have impulse bought just about every pin I've had.

Good point - I hated EMs until I played a well functioning one.

Mars Trek